Question

I have a custom UIButton class that adds a gradient and a gloss effect to the UIButton
the code works perfectly in iOS 4 and on iOS5 simulator but when i run it on iOS 5 devices it gives me the exception EXC_BAD_ACCESS , the exception is triggered by the line :

CGContextStrokePath(context);

any help is really appreciated ,
here’s my code

- (void)drawRect:(CGRect)rect {
    CGContextRef context = UIGraphicsGetCurrentContext();

    CGFloat actualBrightness = _brightness;
    if (self.selected) {
        actualBrightness -= 0.10;
    }   

    CGColorRef blackColor = [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:1.0].CGColor;
    CGColorRef highlightStart = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:0.7].CGColor;
    CGColorRef highlightStop = [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.0].CGColor;

    CGColorRef outerTop = [UIColor colorWithHue:_hue saturation:_saturation brightness:1.0*actualBrightness alpha:1.0].CGColor;
    CGColorRef outerBottom = [UIColor colorWithHue:_hue saturation:_saturation brightness:0.80*actualBrightness alpha:1.0].CGColor;

    CGFloat outerMargin = 7.5f;
    CGRect outerRect = CGRectInset(self.bounds, outerMargin, outerMargin);            
    CGMutablePathRef outerPath = createRoundedRectForRect(outerRect, 6.0);

    // Draw gradient for outer path
    CGContextSaveGState(context);
    CGContextAddPath(context, outerPath);
    CGContextClip(context);
    drawLinearGradient(context, outerRect, outerTop, outerBottom);

    CGContextRestoreGState(context);

    if (!self.selected) {

        CGRect highlightRect = CGRectInset(outerRect, 1.0f, 1.0f);
        CGMutablePathRef highlightPath = createRoundedRectForRect(highlightRect, 6.0);

        CGContextSaveGState(context);
        CGContextAddPath(context, outerPath);
        CGContextAddPath(context, highlightPath);
        CGContextEOClip(context);

        drawLinearGradient(context, CGRectMake(outerRect.origin.x, outerRect.origin.y, outerRect.size.width, outerRect.size.height/3), highlightStart, highlightStop);
        CGContextRestoreGState(context);

        drawCurvedGloss(context, outerRect, 180);
        CFRelease(highlightPath);

    }
    else {
        //reverse non-curved gradient when pressed
        CGContextSaveGState(context);
        CGContextAddPath(context, outerPath);
        CGContextClip(context);
        drawLinearGloss(context, outerRect, TRUE);      
        CGContextRestoreGState(context);

    }
    if (!_toggled) {
        //bottom highlight
        CGRect highlightRect2 = CGRectInset(self.bounds, 6.5f, 6.5f);
        CGMutablePathRef highlightPath2 = createRoundedRectForRect(highlightRect2, 6.0);

        CGContextSaveGState(context);
        CGContextSetLineWidth(context, 0.5);
        CGContextAddPath(context, highlightPath2);
        CGContextAddPath(context, outerPath);
        CGContextEOClip(context);
        drawLinearGradient(context, CGRectMake(self.bounds.origin.x, self.bounds.size.height-self.bounds.size.height/3, self.bounds.size.width, self.bounds.size.height/3), highlightStop, highlightStart);

        CGContextRestoreGState(context);
        CFRelease(highlightPath2);
    }
    else {
        //toggle marker
        CGRect toggleRect= CGRectInset(self.bounds, 5.0f, 5.0f);
        CGMutablePathRef togglePath= createRoundedRectForRect(toggleRect, 8.0);

        CGContextSaveGState(context);
        CGContextSetLineWidth(context, 3.5);
        CGContextSetStrokeColorWithColor(context, [UIColor whiteColor].CGColor);
        CGContextAddPath(context, togglePath);
        CGContextStrokePath(context);
        CGContextRestoreGState(context);
        CFRelease(togglePath);
    }
    // Stroke outer path
    CGContextSaveGState(context);
    CGContextSetLineWidth(context, 0.5);
    CGContextSetStrokeColorWithColor(context, blackColor);
    CGContextAddPath(context, outerPath);
    CGContextStrokePath(context);
    CGContextRestoreGState(context);

    CFRelease(outerPath);

}

what I really wanna now is that is it really related to iOS 5 or am i doing something else wrong ?

Answer 1

The crash happens because the UIColors are already deallocated when you access the CGColorRefs.

An easy way to avoid this is to use

UIColor* blackColor = [UIColor blackColor];
CGContextSetStrokeColorWithColor(context, [blackColor CGColor]);

instead of

CGColorRef* blackColor = [[UIColor blackColor] CGColor];
CGContextSetStrokeColorWithColor(context, blackColor);

so ARC doesn’t get the chance to deallocate the UIColor objects early.